*AMPLITUDE, NAME=EQ, INPUT=Northridge.csv
Run a *FREQUENCY step first to identify the structure's natural frequencies and mode shapes. abaqus earthquake analysis
Unlike static analysis, where inertial ($M\ddotu$) and damping ($C\dotu$) forces are ignored, earthquake analysis in Abaqus solves this full equation. The software utilizes numerical integration schemes (such as the Hilber-Hughes-Taylor method) to solve these equations step-by-step over the duration of the earthquake. *AMPLITUDE, NAME=EQ, INPUT=Northridge